In modern mobile and portable VHF receivers, with IF's in the region of 10 Mhz to 100 MHz for example, with closely spaced channels, the requirements for highly selective IF filters with a good dynamic range are very stringent.
In particular one requirement is that a receiver should be able to work with two different channel spacings, 25 kHz and 12.5 kHz for example.
It has long been realized that crystal filters are particularly useful as IF filters, since they have a very high and stable Q value. While it would be possible to selectively switch into the IF path two separate crystal filters, each specifically designed for one channel spacing, this is an expensive solution, since crystal filter are expensive, and would require additional space in the radio.